Role of eCIRP in Mediating Post-ischemia Microglial Phagocytosis via TREM-2 Receptor: Insights from Porcine and Mouse Cellular Models.

Cerebral ischemia/reperfusion (I/R) injury triggers potent neuroinflammatory responses, in which microglial activation and dysregulated phagocytosis may contribute to neuronal damage. Extracellular cold-inducible RNA-binding protein (eCIRP), a damage-associated molecular pattern, has been implicated in postischemic inflammation; however, its role in regulating microglial phagocytosis remains poorly understood. This study employed a porcine model of cardiac arrest/reperfusion (CA/R) and a mouse cellular model of oxygen-glucose deprivation/reoxygenation (OGD/R) in BV2 microglia and N2a neuron to investigate the role of the eCIRP-TREM2 signaling in microglial activation. We evaluated protein expression and direct interaction between CIRP and TREM2 by Western blotting, immunofluorescence, co-immunoprecipitation, and surface plasmon resonance (SPR), while assessing phagocytic activity by fluorescent microsphere uptake and synaptic protein expression assays. Both CA/R and OGD/R conditions significantly elevated the levels of CIRP expression and activation of the TREM2-DAP12-Syk-ERK1/2 signaling. Treatment with recombinant human CIRP (rhCIRP) further increased the expression of microglial activation markers and enhanced phagocytic activity, accompanied by reducing the expression of synaptic proteins. These effects were partially mitigated by CIRBP or TREM2 silencing, or ERK inhibition. Our findings support a novel hypothesis that eCIRP may bind to TREM2 and activate downstream signaling in microglia, enhancing their phagocytic responses in the process of I/R-induced neuronal injury. The eCIRP-TREM2 axis may thus represent a potential therapeutic target for modulating neuroinflammation and preserving neuronal integrity.